This invention relates to a tape guide mechanism for tape recorder.
For a accurate recording and reproduction, a tape is required to run at a fixed speed and in a proper position relative to a magnetic head. In particular, the tape is expected to run without dislocation of a tape track relative to the magnetic head gap or horizontal or vertical skew. In order to maintain such proper position of the tape as it runs, the tape recorder is provided with a tape guide mechanism. A prior art tape guide mechanism generally includes a pair of tape guides each having a U-shaped notch. These tape guides are arranged on the upper- and lower-course sides of the magnetic head, respectively, along the running direction of the tape. In general, a first tape guide is fixed on the flank of a magnetic head case, while a second tape guide is formed on a head lever spaced from the magnetic head. In such a prior art tape guide mechanism, the first tape guide is located in close proximity to the magnetic head gap, so that it is hard to provide a substantial distance between the tape guides. Since compactness is required of the tape recorder, in particular, it is impossible to keep the tape guides on the head lever fully apart from the magnetic head.
It is a matter of course that the tape guides are essential members to secure tape running in a proper position relative to the magnetic head. Therefore, the tape guides need be manufactured with high accuracy and set in correct positions at assembly. There is not, however, a sufficient distance between the pair of tape guides on both sides of the magnetic head. Accordingly, errors in manufacture or installation of the tape guides, if any, will increase the tilt angle of the tape between the tape guides to greatly affect the dislocation of the tape track or skew of tape, and it will thus be harder to obtain accurate recording and reproduction. Since the first tape guide is formed integrally with the magnetic head case, the case requires high working accuracy and hence increases the cost thereof.
For accurate recording and reproduction, moreover, it is necessary to drive the tape at a constant speed. Generally, the driving force of a motor is transmitted to a flywheel by an endless belt to rotate a capstan shaft with the flywheel. Thus, the tape is held between the capstan shaft and a rotatable pinch roller. For constant-speed tape driving, it is necessary to run the tape in a fixed position between the pinch roller and the capstan shaft, more specifically, a vertically fixed position compared with the pinch roller. In the prior art arrangement, however, no consideration is given to the control of the tape location compared with the pinch roller, and the vertical vibration of the tape cannot fully be prevented.
As an example of a prior art mechanism taking account of the control of the tape location compared with the pinch roller, there may be given U.S. Pat. No. 3,881,187 (Inventor: N. Nakamichi, Patented: Apr. 29, 1975). In this mechanism, a pair of recording heads are arranged severally on both sides of a single reproducing head which is disposed in the center. Further, a pair of erasing heads are arranged on a pinch roller lever outside their corresponding recording heads. Tape guides are fixed to the respective head cases of the reproducing head and the pair of erasing heads. In such an arrangement, although one of the tape guides is located in close vicinity to the reproducing head, the distance between such tape guide and the tape guide on its corresponding erasing head can be set wide. Further, the tape guide on the erasing head can control the tape location relative to its corresponding pinch roller lever. However, the three tape guides are fixed to their corresponding head cases, so that the cases require substantial working accuracy.